The study is aimed at investigating the pharmacodynamic equivalence and the pharmacokinetic bioequivalence of the new BK0023 injectable formulation of filgrastim 0.3 mg/mL by Bio-Ker S.r.l. vs. the comparator (Neupogen® 0.3 mg/mL, Dompé Biotec S.p.A., Italy). Healthy male subjects will receive test and reference at the doses of 2.5 and 5 µg/kg/day for 7 consecutive days and at the dose of 10 µg/kg/day for 5 consecutive days according to a randomised cross-over design. Pharmacodynamics, pharmacokinetics and safety of BK0023 injectable formulation 0.3 mg/mL and of Neupogen® 0.3 mg/mL, administered in 2 consecutive periods with a wash-out of at least 28 days elapsing between the last injection of period I and the first of period II, are compared.